Module busbar arrangement for powerful aluminum electrolytic cells

ABSTRACT

A busbar arrangement for an electrolytic cell utilized for the production of aluminum by electrolysis of molten cryolite salt where the cells are arranged in a side-by-side relationship. In the busbar, the upstream cathode collector and the downstream cathode collector of the upstream cell, the electric connecting arrangements, and the anode risers associated with the downstream cell are combined in the individual busbar modules. In each module, at least one anode riser is situated at the upstream side of the downstream cell and at least one anode riser is situated at the downstream side of the downstream cell. The anode risers at the upstream side are connected to the cathode rods of the upstream and downstream sides of the upstream cell. The anode risers at the downstream side of the downstream cell are connected to the cathode rods and cathode collectors of the downstream side of the upstream cell. The upstream and downstream anode risers are substantially symmetrical about the short planar axis of the cell.

FIELD OF THE INVENTION

This invention relates to aluminum production, in general, and moreparticular to aluminum production by electrolysis of molten cryolitesalts in electrolytic cells arranged in side-by-side relationship.

BACKGROUND OF THE INVENTION

Busbar arrangements for an aluminum electrolytic cells arranged in aside-by-side relationship in the pot room are known in the art. Suchbusbars typically comprise collecting busbars in combination withassociated cathode flexible electrical conductors which are arrangedalong upstream and downstream longitudinal sides of the cell. Anoderisers situated at the upstream side of the cell are provided fortransmitting similar electrical currents there-through. The anodebusbars of the downstream cell are connected to a neighboring upstreamcell by risers. In this manner, the outer risers are connected to theouter cathode collectors of the upstream side of the upstream cell byflexible electrical conductors positioned along the transverse sides ofthe cell. The outer risers are also connected to collecting cathodebusbars or cathode collectors of the downstream side of the upstreamcell.

The intermediate risers are connected to the intermediate cathodecollectors or collecting busbars of the upstream side of the cell by theflexible cathode conductors positioned symmetrically under the cathodeblocks situated in the close vicinity to the end sides of the cell. Theintermediate risers are also connected with cathode collectors orcollecting cathode busbars of the downstream side of the upstream cell.The busbar situated under the bottom of the cell and disposed in thevicinity of the neighboring row of the cells carries 15% of the currentat the upstream side of the cell. On the other hand the other busbarcarries 10% of the current at the upstream side. An intermediate busbaris also situated under the bottom of the cell and extends in to themidpoint between the longitudinal axis of the row of the cells and thecell end on the side opposite to the neighboring row of cells. Thisbusbar carries 5% of the current at the upstream side. The busbararrangement discussed hereinabove is described in French Patent No.2,552,782.

One of the major disadvantages of the above-discussed prior art busbararrangement is limited usage in the high power/amperage electrolyticcells, i.e., electrolytic cells operating with amperage exceeding 350kA. The design of such busbars and risers is subject to variousrestrictions. One such restriction is that the busbars and risers shouldbe arranged so as to minimize the general magnetic field induced in thecell. In particular, the vertical component of such magnetic fieldshould be minimized. The vertical component of the induced magneticfield interacts with the horizontal component of the electric currentsin the molten metal pad giving rise to horizontal forces which canaffect different regions of the metal pad in different ways. Theseforces may result in undesirable metal motion, humping of the metalsurface, and wave formation. These disturbances can necessitatemaintaining larger than required anode to cathode distance in the cell,in turn, increasing the internal resistance of the cell. In operation ofthe busbar, it is important to compensate, the vertical component ofmagnetic field at the ends of the cell by the busbar arrangementsenveloping such ends. The vertical component of the magnetic fielddeveloped at the ends of the working zone of the cell is typicallyformed by the horizontal portions of the anode risers, bus connectorsbetween the anode busbars, and the cathode busbars which extend underthe bottom of the pot. To achieve the optimum magnitude of the verticalcomponent of the magnetic field at the ends of the cell (so as not toexceed 15-20 G) it is often necessary to pass almost the entire currentof the upstream side of the cell through the busbar enveloping the endsof the respective cell. As result, in the aluminum production plant, thebusbars extending from the cathode collector bars of the upstream cellto the anode busbars of the neighboring downstream cell are much longerthan the portions of the busbars of the collector bars at the downstreamside. In order to provide uniform distribution of the current within thecathode collector bars of upstream and downstream sides of the cell andto decrease horizontal currents in the melt, it is necessary to provideequality of resistance in the busbar branches from the cathode collectorbars at the upstream and downstream sides of the upstream cell to theanode busbar of the down-stream cell. Such equality in the resistance isreflected in the Expression [1]. $\begin{matrix}{{R_{{upstr}.} = R_{downstr}}{or}} & \lbrack 1\rbrack \\{\frac{L_{upstr}}{S_{upstr}} = \frac{L_{downstr}}{S_{downstr}}} & \lbrack 2\rbrack\end{matrix}$

Since L_(upstr)>L_(downstr), then it follows that S_(upstr)>S_(downstr).

The sectional area of the busbars from collector bars at the upstreamside is limited by the density of current they carry. The ratio of suchsectional area to the density of the current passing therethrough shouldnot exceed 0.75 A/mm². The sectional area of collector bars at theupstream side is determined by the expression [2].

It should be clear from the above expressions that the higher therequired amperage of the cell, the greater the difference in length ofthe busbar branches at the upstream and down-stream sides, the greaterthe busbar sectional area at the upstream and downstream sides, and as aconsequence, the heavier the busbar. Therefore, in order to accommodatesuch massive busbars, substantial distance is required between the cellsfor the busbar installation. Thus, an aluminum production cell utilizinga busbar fabricated and installed based on the above-discussed prior artprinciples becomes noncompetitive at amperages higher than 350 kA. Atsuch amperages, the weight of the busbars and distance between cellsbecomes prohibitively large.

Patent document SU 1595345 discloses a busbar arrangement forelectrolytic cells arranged in two side-by-side rows. This busbarcomprises the anode busbar connected to the anodes by the anode rods. Italso includes the cathode busbar collectors with the associated cathoderods and flexible electrical connectors extending outwardly at theupstream and downstream sides of the cathode shell. This prior artbusbar also includes connecting busbars which provide connection betweencathode and anode busbars and the busbar of the magnetic fieldcorrection circuit. These elements are disposed in parallel to thetransverse axis of the aluminum electrolytic cell at the ends of thecathode shell. The connection between the cathode busbar of the upstreamcell and the anode busbar of the downstream cell is carried out asbusbar modules consisting of two half-risers. One of the half risers isrigidly connected to the cathode collector at the upstream side of thecell. This side is connected with four flexible electrical connectors.The other half-riser is connected by busbars situated under the bottomof the cathode shell and also connected to the flexible cathodeconnectors at the upstream side of the cell. It should be noted that theconnecting busbars situated under the cathode shell bottom are disposedin parallel to the transverse axis of the aluminum electrolytic cell andin parallel to each other. Electrical current is supplied to thecorrection circuit in the direction coinciding with the direction of thecurrent in the potline. Preferable magnetic field correction current isbetween 20 and 80% of the potline current.

One of the disadvantages of the prior art busbar discussed in SU 1595245is utilization of the independent magnetic field correction arrangement.The arrangement consists of two conductors extending along both ends ofthe cells in the circuit in the direction of potline current. Thecorrection current is between 20 and 80% of the potline current. Forexample, with the potline current at the level of 500 kA, the correctioncurrent can be as high as 400 kA. The busbar arrangement is heavy due tothe presence of the above-discussed corrective busbars. The additionalweight is about 14 tons for each electrolytic cell. Utilization of theabove-discussed heavier correction circuits causes an increase in theelectric power consumption due to the voltage drop in the correctioncircuit. All of the above ultimately result in increased costsassociated with construction and maintenance of the production areasassociated with the correction circuits. For example, when the amperageis at the level of 400 kA, the correction busbars arrangement mayconsist of 16 busbars each having cross-sectional area of 650×70 mm. Thetotal width of such massive busbar arrangement is about 2 meters.

The passage of the electric current in the power supply conductors andin the conducting portions of the cell generates magnetic fields whichcause undesirable movements in the liquid bath which causes deformationof the metal-electrolysis bath interface. These movements of metalagitate the electrolytic bath placed underneath the anodes and canshort-circuit this element of the bath when contact occurs between theliquid metal and the anode. In such instances the electrolysis yieldgreatly diminishes and power consumption increases.

It is known that the metal-bath interface and the movements of theliquid metal are closely dependent on the values of the verticalcomponent of the magnetic field and symmetry of the horizontalcomponents. Minimizing the value of the vertical component in themagnetic field causes substantial reduction in the depth between thehighest and lowest points of the metal layer and reduction of themagnetic forces which cause disturbances in this layer. Thus, it ishighly desirable to minimize the vertical component of the magneticfields in the liquid metal and to reduce the circulation of liquid metaland of liquid bath in the cell.

One of the objects of the invention is to reduce operational costs byincreasing unit capacity of an electrolytic cell by increasing theamperage and decreasing the busbar weight.

Another object of the invention is to mitigate adversemagneto-hydrodynamic effects in the melt, to eliminate the correctioncircuit, to optimize the magnetic field and to reduce specific electricpower consumption. A further object of the invention is to provide anarrangement capable of placing the cells as close to each other aspossible. This is highly desirable in order to reduce specificoperational costs for the potrooms and to retain sufficient free accessfor personal movement and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of the cell modules of the invention;

FIG. 2 is a cross-section view showing two adjacent cells illustratingconveyance of current from upstream to downstream cells in the module ofthe invention;

FIG. 3 is a graph illustrating a perspective view of the verticalcomponent (Bz) of the magnetic field at the metal pad of the cell havingthe busbar configuration of FIGS. 2 and 3;

FIG. 4 is a graph illustrating distribution of the vertical magneticfield component (Bz) in the metal pad according to the invention, withno current being provided in the down-stream anode risers of thedownstream cell;

FIG. 5 is a graph illustrating distribution of the vertical magneticfield component (Bz) in the metal pad according to the invention, withno current being provided in the upstream anode risers of the downstreamcell;

FIG. 6 is a graph illustrating distribution of the vertical magneticfield component (Bz) in the metal pad according to the invention, withthe electrical current being provided in the upstream and downstreamanode risers of the downstream cell; and

FIG. 7 is a schematic diagram showing the upstream and downstream cellsin the module of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1, 2, and 7, which show the electrolytic cellsdisposed transversely in rows with their long sides situatedperpendicular to the general direction of the current. The elements ofthe invention are referred to as upstream or downstream, depending onwhether they are originated from the upstream or the downstream side ofthe respective cell or within the row of cells, with respect to thedirection of the current which is taken as the reference.

FIG. 1 illustrates an arrangement with large numbers of electrolyticcells laid out in lines in the electrolysis pot rooms electricallyconnected in series using connecting conductors in order to optimize theoccupancy of factory floors. It is further illustrated in FIG. 1 thatthe cells are arranged so as to form least two parallel lines which areelectrically connected to each other by the conductors. The electrolysiscurrent therefore passes in the cascade fashion from one cell to thenext. The length and mass of the conductors should be as small aspossible in order to limit investment and operating costs. Theconductors are also configured such as to reduce or offset the effectsof magnetic fields produced by the electrolysis current.

As illustrated in FIG. 7, the “right-hand head of the cell” refers tothe side of the cell situated on the right-hand side of an observerplaced in the axis of the line of cells and looking in the direction ofthe current traversing this line of cells. The term “left-hand head ofthe cells” refers to the other side of the cell.

As best illustrated in FIGS. 1, 2 and 7, aluminum electrolytic cells arestructures having long or longitudinal axis Y-Y and short or transverseaxis X-X. Each cell comprises a metal casing or a cathode shell 8 whichis formed with a bottom portion 21 and side portions 22, 23 extendingoutwardly therefrom. An interior of the shell 8 is lined with insulatingmaterial adapted to support a cathode assembly which is formed by aplurality carbonaceous blocks 24. Embedded in the carbonaceous blocksare cathode metal collector bars 4 extending within the celltransversely to the longitudinal axis Y-Y. The cathode metal bars 4 areelectrically connected at one end to a negative conductor or cathodeconnecting conduit 6 and at another end to a cathode connecting conduit7. The connection between the cathode collector bars 4 and the cathodecollectors 6 and 7 is by means of flexible electrical conductors 5.Fixed on the shell 8 is a superstructure containing an anode assemblycomprising anode busbars 1 extending along the longitudinal axis Y-Y ofthe cell. Carbon anodes 2 are suspended from the anode busbars by meansof metal anode rods 3.

The arrangement of the invention is subdivided into a plurality ofbusbar modules. In this respect FIG. 1 illustrates the busbar subdividedinto four modules: A, B, C, and D. Each module comprises an anodebusbars assembly with the metal anode rods 3 adapted for supplyingcurrent to the carbonaceous anodes 2. In each module the upstream cellis formed with the upstream cathode collector 6 disposed at the upstreamside of the upstream cell and the downstream cathode collector 7provided at the downstream side thereof. The cathode bars 4 by means ofthe flexible electrical conductors 5 are connected to the respectivecathode collectors 6 and 7.

As best illustrated in FIGS. 1 and 2 each cell is formed with twoparallel lines of anodes 2 supported by the rods 3. The anode busbar 1is formed by upstream and downstream bar elements 1A and 1Brespectively, connected by equi-potential rods. The anode busbars 1 ofthe downstream cell receive the current collected by the cathode rods 4through the upstream 6 and downstream 7 cathode collectors of theupstream cell. The current is transferred by means of connecting busbars9 to the upstream riser 10 of the downstream cell. The risers or risingconnections 10 and 11 are typically formed having horizontal andvertical portions, so as to rise over the ends or over the respectivesides of the cell, forming the elevated structures ultimately connectingthe anode busbars 1 of the downstream cell and the cathode collectorbusbars 6, 7 which are disposed lower around the upstream cells. Eachupstream riser 10 is formed having double-branch structure. Morespecifically, each raiser 10 comprises a branch 10A connected to thedownstream cathode collector 7 of the upstream cell and a branch 10Bconnected to the upstream cathode collector 6 by at least one connectingbusbar 9 passing under the bottom of the cell.

In each module the anode busbars 1 and ultimately the anodes 2 aresupplied with electrical current by means of the risers 10 and 11 whichare positioned symmetrically to the short or transverse axis X-X of thecell. As illustrated in FIG. 1, the upstream anode risers 10 associatedwith the upstream side 1A of the anode busbar of the downstream cell areconnected to the cathode rods 4 and the respective cathode collectors 6and 7 of both the upstream and downstream sides of the upstreamelectrolytic cell. The downstream anode risers 11 associated with thedownstream side 1B of the anode busbar are connected to the cathode rods4 and the downstream cathode collector 7 of the upstream cell. Theelectric connecting busbar or arrangements 9 are disposed primarilyunder the bottom portion 21 of the cathode shell 8. Portions of theconnecting arrangements 9 of the outer busbar modules A and D envelopthe end areas of the respective electrolytic cell, so as to extendsubstantially vertically approximately up to the level of molten metalin the cell.

FIGS. 1 and 2 illustrate an embodiment of the busbar arrangement of theinvention having risers 10 associated with the upstream side 1A of theanode busbar connected to about ⅔ of the collector bars of the busbarmodule. The risers 11 at the downstream side 1B of the anode busbar areconnected to about ⅓ of collector bars of the busbar module.

Although the busbar arrangement of the invention is illustrated in FIG.1 as having four busbar modules, a busbar arrangement consisting of anyreasonable number of busbar modules depending on the required power ofthe cell is within the scope of the invention.

In the busbar arrangement of the invention operates in the followingmanner. By means of the flexible electrical conductors 5 the electricalcurrent in the upstream cell is directed from the cathode rods 4 to therespective upstream 6 and downstream 7 cathode collectors. Thehorizontal sections of the upstream anode risers 10, as well as theelements associated with the respective upstream cell, such as theconnecting busbars 9 extending under the bottom of cathode shell 8, thecathode rods 4 and the respective flexible electric conductors 5 at thedownstream side create in the metal-electrolysis bath interface avertically oriented component or vector of the magnetic field (Bz). Morespecifically, this vertically oriented component of the magnetic field(Bz) is directed upwardly in the left hand head of the electrolytic cell(according to direction of the current in the potline). This verticalcomponent of the magnetic field is directed downwardly in the right handhead of the cell. The horizontal sections of the downstream anode risers11, the connecting busbars 9 of the outer modules A and D, and thecathode rods 4 with the respective flexible electrical conductors 5 atthe upstream side of the upstream cell create in the melt the verticalcomponent of the magnetic fields (Bz) having orientation opposite tothat of the above discussed conductors. That is, the vertical componentof the magnetic field (Bz) is directed downwardly at the left hand headof the cell and upwardly at the right hand head of the cell. Mutualcompensation of the magnetic field (according to the axis Bz) from bothgroups of the above-discussed conductors assures the optimum value ofthe magnetic field which does not exceed 15-20 G. Significantly, theanode risers 11 associated with the downstream side 1B of the anodebusbar eliminate the necessity to install the independent lines ofconductors adapted for the correction the magnetic field, as discussedby the prior art.

Each horizontal section of the upstream risers 10 and downstream risers11 create in the melt on the right side from their location (accordingto the direction of the electrical current in the riser) a magneticfield directed downwardly relative to the axis (Bz) and directedupwardly relative to the (Bz) axis on the left side from their location.This arrangement provides for frequent sign alternation (positive ornegative) according to the direction of the vertical component of themagnetic field extending along the longitudinal sides of the cell. Asillustrated in FIG. 1, the upstream risers 10 and downstream risers 11associated with upstream branch 1A and the downstream branch 1Brespectively are positioned opposite each other. Thus, the signalteration relative to the axis (Bz) along the longitudinal sides of thecell is asymmetric about planar axes of the cell. In each module thecurrent distribution in the anode risers is chosen in such a manner thatthe maximum value of the magnetic field in the melt does not exceed15-25 G.

The electrical current distribution in the upstream anode risers 10 ofthe downstream cell is between ½ and ¾ of the module current. Theelectrical current distribution in the downstream anode risers 11 of thedownstream cell is between ½ and ¼ of the module current. The abovearrangement provides the relative equality of the volume and transverseelectromagnetic forces in the metal. This enhances development of thesymmetric metal pad topography, symmetric ledge, and freeze in the workzone, so as to improve positive effect on MHD stability of the melt.Relatively small anode-cathode distance in the module and relativelysmall weight of the busbar are accomplished in view of the fact that thecurrent is transferred in the shortest distance from the upstream to thedownstream cell. This also occurs in view of the similarity in thelength between the busbar branches disposed at the upstream anddownstream sides of the cell. The above discussed arrangement enablesthe invention to provide in the busbar branches the maximum permissibleelectrical current density, while maintaining the minimum cross-sectionarea thereof.

In the invention, the modular design makes it possible to develop abusbar arrangement adaptable for the amperages of 500 kA and greater,while maintaining a relatively small weight. Magnetic field optimizationis based on the following principles. The vertical component of themagnetic field (Bz) acts on the molten metal layer is of the samedirection (positive or negative) over a substantial area of the cell(particularly along its longitudinal axis) forming coherent andincreased oscillation of the molten metal surface. This occurs becauseof the longitudinal moment buildup along the cell. Therefore, in thepresent invention, the magnetic field is optimized by frequent signalterations along the vertical component (Bz). This occurs at leastalong the longitudinal sides of the cell, where the signs are alteredfrom positive to negative and negative to positive, relative to theplanar axes of the cell.

As illustrated in the diagram of FIG. 3, the module busbar of theinvention creates in the melt nine the sign alternations according tothe direction of the vertical component (Bz) of the magnetic field atthe upstream side, and eleven sign alternations at the downstream side.The magnetic field according to the axis (Bz) is asymmetrical relativeto the planar axes of the cell and does not exceed 25 G.

Utilization of the above-discussed busbar of the invention results inincreased capacity of the cell. This is achieved in view of the amperageincrease to the level up to 500 kA and higher, while maintaining theefficiency of between 93% and 95% and specific electric powerconsumption between 12300 and 13500 kWh/t.

Example 1

FIG. 4 illustrates distribution of the vertical magnetic field component(Bz) as depicted in the melt of the electrolytic cell with no currentbeing provided at the anode risers on the downstream side 1B of theanode busbar of the downstream cell. This figure actually illustrates anexperimental example of the calculated magnetic induction vector (Bz) ofthe electrolytic cell having the busbar arrangement of the invention. Inthis example the electrical current in the anode risers at thedownstream side 1B is equal to zero. The current provided by the anoderisers 10 to the upstream side 1A of the busbar is equal topredetermined values. It is apparent from the graph in FIG. 4 that the(Bz) component of the magnetic field from the risers 10 that it isaccumulated at the ends of the cell can reach the value up to ±50 G. Themagnetic field from the busbars enveloping the ends of the cell isinsufficient to compensate the vertical (Bz) component generated by theupstream risers 10. The magnetic field from the side of the risers is ofthe wave nature, whereas at the opposite side it changes almostlinearly.

This example resembles a typical situation in the prior art anode busbarstructures for the side-by-side cell arrangement. In the prior art themagnetic field at the ends of the cell is typically compensated by themagnetic field from the stack plates enveloping the ends of the cell.However, the prior art method of compensation causes substantialincrease in the weight of the busbar and leads to the increase in thedistance between the cells. There is also known compensation pattern bymeans of individual conductors extending along the short side of thecell and directed along the direction of current running in the potline.In this instance, the amperage is between 80 and 120 kA. This prior artmethod of compensation is expensive and requires additional powersupplies.

Example 2

FIG. 5 illustrates another experimental example of the calculatedmagnetic induction vector Bz of the electrolytic cell utilizing thebusbar arrangement of the invention. The current in the anode risers atthe upstream side 1A is zero. The current in the anode risers 11 at thedownstream side 1B is equal to the predetermined values. It is apparentfrom the graph of FIG. 5 that the Bz component of the magnetic field isaccumulated from the anode risers 11 at opposite ends of the cell, so asto reach value up to ±50 G. The magnetic field at the risers 11 is ofthe wave nature, while at the side opposite to the risers the magneticfield changes almost linearly.

Example 3

FIG. 6 represents a graph illustrating an example of distribution of thevertical magnetic field component (Bz) according to the invention withthe electrical current being provided in the upstream 10 and downstream11 anode risers. It is shown in this graph that the sign of the verticalcomponent (Bz) of the magnetic field alternates many times in thedirection along the longitudinal sides of the cell. The alternationsindicated by the “+” and “−” signs are asymmetrical relative to the longaxis of the cell. In this example the value of the component (Bz) doesexceed ±25 G.

There are many benefits of positioning the risers on both upstream 1Aand down-stream 1B sides of the anode busbar, in accordance with theinvention. In the arrangement of the invention it is not necessary tocompensate the magnetic induction vector (Bz) at the cell ends byproviding individual busbars or busbars enveloping the ends of the cell.This results in substantial reduction of the weight of the busbar. Theasymmetrical and multiple alternations of the sign of the verticalcomponent (Bz) along longitudinal sides and the desirable range of itsvalue (which does not exceed 20 G) are the prerequisites of stable celloperation at the amperage of 500 kA and higher. Unlike the prior art,the current to the anode risers 10 at the upstream side 1A of thedownstream cell is directed from the upstream cathode collectors 6 andthe cathode bars 4 of the upstream cell, while the current to the anoderisers 11 at the downstream side 1B of the downstream cell is deliveredfrom the downstream cathode collectors 7 and cathode bars 4 of theupstream cell. This arrangement assures the relative equality in thelength of the most busbar branches and makes it possible to maintain thehighest possible current density and also to reduce the total weight ofthe busbar. The modular type of the busbar of the invention facilitatesassembly from such modular and electrolytic cells having practically anyrequired power.

In the production of aluminum by electrolysis of molten cryolite saltsin the electrolytic cells arranged in the side-by-side relationship in apot room, it is essential to increase unit capacity of a cell byincreasing the amperage, decreasing the busbar weight, so as toultimately reduce the operational costs. In the invention, these objectsare achieved by providing the busbar assembly where the upstream cathodecollectors 6 and the downstream cathode collectors 7 of the upstreamcell; the electric connecting arrangements or connecting busbars 9, andthe anode risers 10 and 11 associated with the downstream cell arecombined in the individual busbar modules. In the invention, in eachmodule at least one anode riser 10 is situated at the upstream side 1Aof the downstream electrolytic cell and at least one anode riser 11 issituated at the downstream side 1B thereof. The anode risers 10 at theupstream side 1A are connected to the cathode rods 4 and cathodecollectors 6 and 7 of the upstream and downstream sides of the upstreamcell. The anode risers 11 at the downstream side 1B are connected to thecathode rods 4 and the cathode collector 7 of the downstream side of theupstream cell. Each busbar module of the invention is adapted forpassage between 10 and 100% of the pot line electrical current. In thepreferred embodiment each busbar is adapted for passage between 18 and30% of the pot line electrical current. The anode risers 10 at theupstream side 1A are arranged to distribute between 50 and 75 percent ofthe module current. On the other hand, the anode risers 11 at thedownstream side 1B are arranged to distribute between 50 and 75% of themodule current. The anode risers 10 and 11 are substantially symmetricalabout the short planar axis of the cell. The electric connectingarrangement or connecting busbars 9 are disposed under the bottomportion 21 of the cell. At least a portion of the connecting busbars 9of the outer modules (modules A and D, for example) envelops the endareas of the respective cells, so as to be located, at least, at thelevel of the molten metal. The number of the cathode rods 4 connected tothe electrical connecting arrangements 9 on the portion of the cellclosest to the neighboring row of the cells exceeds the number of thecathode rods connected to the electrical connecting arrangements 9 onthe opposite side.

1. A busbar arrangement for electrical connection between two successivecells in a series of cells arranged in two rows in a side-by-sideconfiguration and adopted for the production of aluminum byelectrolysis, comprising: an upstream cell and a downstream cell, ananode busbar of at least said downstream cell connected to anodes byrespective anode bars, said anode busbar having an upstream side anddownstream side; a cathode busbar of at least said upstream cellcomprising a plurality of cathode rods extending outwardly from acathode shell for connection with respective upstream and down-streamcathode collecting conduits, flexible electrical conductors beingprovided between said cathode rods and the respective upstream anddownstream cathode collecting conduits; and a plurality of currentsupply conductors or risers associated with the anode busbar of thedownstream cell; and said busbar arrangement further comprising upstreamand downstream cathode collecting conduits of the upstream cell,connecting busbars, the anode risers associated with the downstream cellare joined so as to form a plurality of integral busbar modules; in eachsaid module at least one anode riser is associated with the upstreamside and at least one anode riser is associated with the downstream sideof the anode busbar of the downstream cell; said at least one anoderiser at the upstream side of the downstream cell is connected to thecathode rods and the respective upstream and downstream cathodecollecting conduits of the upstream cell, whereas said at least oneanode risers at the downstream side of the downstream cell is connectedwith the cathode rods and the respective downstream cathode collectingconduit of the upstream cell.
 2. The busbar arrangement of claim 1,wherein each said module is adapted for passing between 10 and 100percent of the potline current.
 3. The busbar arrangement of claim 2,wherein each said module is adapted for passing between 18 and 30percent of the potline current.
 4. The busbar arrangement of claim 1,wherein said at least one anode risers at the upstream side is adaptedto distribute between ½ and ¾ of the module current.
 5. The busbararrangement of claim 4, wherein said at least one anode risers at thedownstream side are adapted to distribute between ½ and ¼ of the modulecurrent.
 6. The busbar arrangement of claim 1, wherein said at least oneupstream and down stream anode risers are symmetrical about the shorttransverse axis of the downstream cell.
 7. The busbar arrangement ofclaim 1, wherein said connecting busbars are disposed under a bottomportion of said upstream cell and at least a portion of the connectingbusbars of the outer modules envelopes the end portion of the respectivecell, so as to extend at least at the level of molten metal in saidcell.
 8. The busbar arrangement of claim 1, wherein there are morecathode rods at the upstream side connected to the collecting busbars atthe portion of the cell closest to the neighbor row than the connectingbusbars at the other end.
 9. The busbar of claim 1, wherein the electricconnecting busbar is disposed under the bottom portion of the cell andat least a portion of the connecting busbar of the outer modulesenvelopes the end areas of the respective cells so as to be located atleast at the level of the molten metal within the cell.
 10. The busbararrangement of claim 1, wherein a vertically oriented component of themagnetic field Bz is directed upwardly in a left hand head of theelectrolytic cell, according to direction of the current in the potline,said vertical component of the magnetic field is directed downwardly inthe right hand head of the cell.
 11. The busbar arrangement of claim 10,wherein horizontal sections of said at least one downstream anode riser,the connecting busbars of the outer modules, and the cathode rods withthe respective flexible electrical conductors at the upstream side ofthe upstream cell create in the melt the vertical component of themagnetic fields Bz directed downwardly at the left hand head of the celland upwardly at the right hand head of the cell.
 12. The busbararrangement of claim 1, wherein each horizontal section of said at leastone upstream riser and said at least one downstream riser create in themelt on the right side from their location, according to the directionof the electrical current in the riser, a magnetic field directeddownwardly relative to the axis Bz and directed upwardly relative to theaxis Bz on the left side from their location.